This application claims priority to Japanese patent application serial number 2002-361478, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to throttle bodies that have throttle valves actuated by motors for controlling the rotational speed of internal combustion engines. In particular, the present invention relates to throttle bodied that have metal plates for supporting gear shafts of gear mechanisms that transmit rotation of motors to throttle valves.
2. Description of the Related Art
There are known throttle bodies that have motor actuated throttle valves. For example, Japanese Laid-Open Patent Publication No. 2001-303983 teaches a throttle body in which a throttle valve, a throttle shaft, a motor, and a gear mechanism, are disposed. The throttle body of this publication is used as an automobile part and is modified to provide a lightweight structure by using resin as the material of the throttle body. The throttle valve is secured to the throttle shaft and the motor rotatably drives the throttle shaft. A gear mechanism, comprising a plurality of gears and gear support shafts, serves to transmit the driving force of the motor to the throttle shaft.
However, by using a resin material for the throttle body, potential deformation of the throttle body may occur due to residual molding stress and/or strain or due to forces applied to the throttle body during the assembly process. This deformation could cause a change in the relative distances between the gear shafts. As a result, the gear teeth may be unintentionally stressed, resulting in excessively wear and rough operation of the gears. Therefore, in order to solve these problems, the above publication proposes to use a single metal plate in order to support all of the gear shafts.
However, there still exists a possibility of deformation because the metal plate must be relatively large in order to support all of the individual gear shafts. The deformation can occur when the metal plate is secured to the throttle body or during the molding process of the throttle body itself, since the throttle body is formed integrally with the metal plate as an insert molding process. Unfortunately, a problem exists in that it is very difficult to correct any changes in the distance caused due to the deformation of the metal plate. In addition, use of a relatively large sized metal plate may result in increased material costs.
It is accordingly an object of the present invention to teach improved techniques for reducing the material cost of a throttle body and facilitating correction of distance between gears of a gear mechanism of the throttle body.
According to one aspect of the present teachings, throttle bodies include a main body made of a lightweight material; preferably resin, for example, ABS resin. A throttle valve, a motor, and a gear mechanism, are disposed within the main body, so that the rotation of the motor is transmitted to the throttle valve via the gear mechanism. The gear mechanism includes a drive gear mounted to an output shaft of the motor and an intermediate gear disposed between the drive gear and the throttle valve. A metal plate, e.g., preferably a steel plate, is mounted to a motor casing of the motor and the intermediate gear is mounted to the metal plate. An adjusting device serves to adjust the position of the intermediate gear laterally across a face of the main body.
Because the throttle gear is mounted to the metal plate that is in turn mounted to the motor casing, the distance between the drive gear of the motor and the intermediate gear can be reliably maintained to a suitable length. In addition, because the adjusting device can adjust the position of the intermediate gear laterally across the face of the main body, the position of the intermediate gear relative to an element that is mounted on or supported by the main body can be suitably adjusted. In particular, the position relative to a throttle gear that engages the intermediate gear can be adjusted. As a result, any undesired wear of the gears within the gear mechanism due to the incorrect spacing of gears could be reduced or minimized. In addition, because the metal plate only supports the intermediate gear and is mounted to the motor casing, the metal plate may have a relatively small overall size. Therefore, the throttle body can be manufactured at a lower cost while still providing overall improved controllability of the throttle valve.
In still another aspect of the present teachings, throttle bodies further include a fixing device that serves to fix the metal plate in position relative to the main body. In this construction, it is advantageous that the adjusting mechanism serves to adjust the relative position between the metal plate and the main body in order to adjust the position of the intermediate gear relative to an element that is mounted on or supported by the main body. With this construction, the positions of the drive gear and the intermediate gear can be simultaneously adjusted relative to the main body.
Preferably, the metal plate is fixed in position relative to the motor casing and the intermediate gear is rotatably mounted on a gear shaft that is secured to the metal plate.
In further aspect of the present teachings, the fixing device comprises a screw(s) and the adjusting mechanism comprises at least one mounting hole formed in the metal plate. The mounting hole(s) is(are) adapted to receive the fixing device and in one aspect has an elongated configuration having a length that is greater than the width of the mounting hole. Therefore, the adjusting mechanism may have a relatively simple configuration and a relatively low number of parts.
Preferably, the mounting hole(s) is(are) elongated in a circumferential direction substantially about the output shaft of the motor.
Preferably, the screw (s) engages a threaded hole(s) that is(are) formed in the main body.
In a still further aspect of the present teachings, the gear mechanism additionally includes a throttle gear that is coupled to the throttle valve and is rotatable with the throttle valve. The throttle gear engages the intermediate gear. Therefore, by adjusting the position of the intermediate gear, the interface between the intermediate gear and the throttle gear may be suitably established.